import java.util.*;
public class Main{
    public static long num(int n){
        long[]f=new long[32];
        f[1]=1;
        f[2]=1;
        for(int i=3;i<32;i++){
            f[i]=f[i-1]+f[i-2];
        }
        return f[n];
    }
    public static void main(String[]args){
        Scanner scan=new Scanner(System.in);
        int n=scan.nextInt();
        System.out.println(num(n));
    }
}
